Pheromone Processing: Verts

• epithelium in the nose is made up of receptors and supporting with cells with cilia at the surface • air or water carries odourants over the epithelium • proteins in the cilia catch odour molecules • OSNs synapse directly to brain

• olfactory epithelium: organized into 4 zones by type of receptor • main olfactory bulb: OSNs converge here in similar zones • neighbouring areas in the MOB process similar odourants based on chemical structure

• odourant • odourant binding protein • main olfactory epithelium • main olfactory bulb • olfactory tract • cortex (elaborate)

• anterior olfactory nucleus - contralateral olfactory bulb • lateral amygdala - hypothalamus • entorhinal cortex - hippocampus • piriform cortex - thalamus - orbitofrontal • piriform cortex - frontal cortices

• pheromone • pheromone binding protein • vomeronasal organ (basal and apical) • accessory olfactory bulb (posterior and anterior) • medial amygdala • hypothalamus

• mitral and tufted - local inhibitory neuron called granule cells

• GABA is released from granule cells to inhibit mitral cells • glutamate is released from mitral cells to excite granule cells

• position the molecule is in (ie. fire for para position no matter what chain length) • chain length (ie. fire for short chain length no matter what position) • different glomeruli detect different molecular features

• sometimes simultaneous input is needed from two different glomeruli/mitral cells to have activation in the olfactory cortex • input from one or the other is not sufficient

• vomeronasal has two sections of epithelium (apical sensory neurons and basal sensory neurons) • apical project to the anterior AOB • basal project to the posterior AOB • two zones in AOB

• lateral amygdala: social behaviour and emotions • hypothalamus: homeostasis and reproduction • hippocampus: memory • piriform cortex: identification of odours • neocortex: conscious discrimination of odours

• topography apparent in epithelium and glomeruli of main olfactory bulb • not much topography in cortical areas: • anterior olfactory nucleus: preserves dorsal-ventral topograpy • cortical amygdala: overlapping terminal fields • piriform cortex: none

• vasopresson neurons found in main and accessory olfactory bulbs and anterior olfactory nucleus • vasopression is important for social recognition and complex social behaviours • vasopressin neurons may filter out social odours • a possible mechanism: release of primed vasopressin causes inhibition of firing for neurons representing familiar odour

• young mice produce exocrine-gland secreting peptide 22 (ESP22) • secrete from lacrimal gland and tears • activates high-affinity receptors in vomeronasal organ and downstream limbic neurons in the medial amygdala • exerts powerful inhibitory affects on males

• odourant • odourant binding protein • olfactory receptor • activates g protein • activates adenylyl cyclase • ATP to cAMP • binds to cation channels (CNGCC) • influx of Ca and Na • Ca gated chloride channel • efflux of chloride • membrane depolarized

• usually we would expect to see a chloride influc because there is more chloride on outside of the membrane • however here there is a chloride efflux that strengthens depolarization

• Pezier at al.: looked at affect of blocking the chloride channels and decreasing the external chloride concentration which caused a delay; concluded that they are used for repolarization • Billig et al: chloride channels were identified as Anoctamin2 in the MOE and VNO, disruption in mice did not impact them greatly

• receive pheromone input from the main olfactory epithilium <1%

• pheromone • receptor • activates g protein • activates guanylyl cyclase • increase in cGMP • cGMP gated cation channel • Ca and Na influx • Ca-gated chloride channel • chloride efflux

• pheromone • receptor • activate g protein • activate phospholipase C • produces IP3 and DAG • both activate cation channels • Ca influx (possible Cl efflux)

• Vosshall et al. • may act as pheromone in people • is a break down product of testosterone and acts as pheromone in other animals • three variants of receptor OR7D4 which responds to androstenone • most common: sickening scent • second: sweet smell • third: unable to detect

• TRPC2 receptor in some primates (replaced by trichromatic vision except in one primate with both) • pheromone receptor gene V1rl1 found in olfactory mucus • have looked at cadivers but no evidence

• relatively unknown • odourant can bind to multiple receptors based on different characteristics (shape and ‘colour’) producing an olfactory code or reaction pattern • characteristic pattern of hydrogen bonds between odourant and receptors • vibrational mode (electron transport from donor to acceptor) may also play a role in recognition